1. Field of the Invention
This invention relates in general to valves for controlling fluid flow. More particularly, the invention relates to valves for controlling the release of a high pressure fluid such as gas contained in a pressure vessel with the valve being secured against leakage over long periods of time.
2. Description of the Related Art
In aerospace and other applications it is frequently necessary to establish a secure, non-leaking, seal of a gas under high pressure over a long period of time and then subsequently release the gas for use in its intended purpose. Examples include spacecraft with pressure vessels containing propellant gases needed for deceleration and attitude control. The pressurized gases must be secured against leakage for years before the spacecraft reaches its destination at which time the propellant must be released. Ordinary release valves in general do not seal well enough to contain pressurized gas over long periods of time.
Heretofore spacecraft have been provided with "pyrovalves" which enable secure gas seals. However, such valves are activated by means of explosives to rupture welded lines which are in communication with the pressure vessels. Because of the great force created by the explosions when the pyrovalves are actuated, they have disadvantages from the standpoint of safety, weight, reliability and mechanical shock to the spacecraft.
The need has therefore been recognized for a release valve which can maintain a fluid pressure seal over long periods of time and which obviates the foregoing and other limitations and disadvantages of the prior art valves of this type. Despite the various release valves in the prior art, there has heretofore not been provided a suitable and attractive solution to these problems.